Hypodermic injector



i April v1.6,;1946. M, 1 LocKHART 2,398,544

HYPODERMIC INJECTOR FiledJan; 6, 1945 BYZ ai Patented Apr. 16, 1946 UNITED STATES PATENT OFFICE HYPODERMIC INJECTOR Marshall L. Lockhart, Detroit, Mich.

Application January 6, 1945, Serial No. 571,679

(Cl. 12B-215) 9 Claims.

My present invention relates to a hypodermic injector having improved operating characteristics when compared with the injector shown in my co-pending application, led March 15, 1943, Serial No. 479,183 now Patent No. 2,380,534.

One object of the invention is to provide a hypodermic injector of the type wherein spring means is used to effect discharge of hypodermic liquid with suiiicient force to cause self-injection thereof, the pressures produced being such that initially there is a sudden build-up of the pressure to cause the liquid to puncture the skin, and thereafter the pressure drops oi considerably, but still remains high enough to keep the liquid iiowing through the puncture made in the skin and enter the tissue therebeneath during expulsion of al1 of the liquid from the injector.

Another object of the invention is to provide a hypodermic injector having a moving plunger for expelling liquid from the instrument, the plunger, however, being concealed within the casing of the instrument to eliminate any psychological effect caused by the patient being able to see the movement of the plunger, as in my application, Serial No. 479,183, hereinbefore referred to.

An additional object is to provide a means for readily cocking the injector or compressing the spring therein and latching the plunger in retracted position, this means being also operable to effect release of the plunger.

Still another object is to provide the releasing means for the plunger operable upon a predetermined pressure applied thereto, and to arrange the parts of the instrument, so that such pressure is transmitted through the instrument to the patient to thereby insure proper contact of the instrument with the patient while making the injection.

With these and other objects in view, my invention consists in the arrangement, construction and combination of the various parts of my hypodermic injector, whereby the objects contemplated are attained, as hereinafter more fully set forth, pointed out in my claims, and illustrated in the accompanying drawing, in which:

Fig. 1 is a full size elevation of a hypodermic injector embodying my present invention.

Fig. 2 is an enlarged, longitudinal sectional view through the same, showing it in cocked position.

Fig. 3 is a similar, sectional view, showing the instrument in released position and accomplishinga hypodermic injection; and

Fig. 4 is a sectional view on the line I-I of Fig. 2, to illustrate details.

On the accompanying drawing, I have used the reference character C to indicate generally a casing, S, a sleeve thereon, and A, an ampule held against one end of the casing by a collar i0. The ampule A comprises briey, a body portion having a ilange l2, a bore Il, a minute oric I6, and a spicule i8. Initially the oriiice I3 is closed by the spicule il and the spicule is capable of being broken off for thereby opening the orlilce. The ampule may be molded of a suitable plastic material. The orifice I6 is very small in size, such as .003 to .005 inch.

The collar l0 is screwed on the casing C, as illustrated, to hold the bore I 4 in proper alignment with a perforation I8' in the lower end of the casing C. Through this perforation and into the bore, a plunger 20 is adapted to extend for displacing liquid from the ampule A. The plunger 20 has a shoulder formed by a collar 22, and above this collar a spring 24 is mounted in the casing C. A cap 26 on the casing confines the spring in position.

The spring 2l when in the position of Fig. 3

is expanded in relation to its position in Fig. 2, but even in Fig. 3 is under compression. In other words, it is pre-loaded or initially longer than the distance between the collar 22 and the cap 26 in Fig. 3, so that when the cap is screwed into position, the spring is under considerable compression.

The sleeve S has an inward projection in the form of a cross piece 2l, passing through opposite slots 2li in the casing C. This cross piece has a. bore 32, through which the plunger extends, and the cross piece is held assembled relative to the sleeve by a pair of screws 3l. The cross piece has a shoulder, indicated at 36, which upon movement of the sleeve upwardly in Fig. 3, engages the collar 22 to the left of the plunger, thereby lifting the plunger, and at the same time tending to swing the lower end thereof toward the left. Consequently when the sleeve is pulled all the way up, the lower end of the plunger swings onto a shoulder Il of the casing C surrounding the perforation Il. The plunger is thereby latched in raised position or cocked During the cocking action, it will be obvious that the shoulder 36 of the cross piece 28 serves as a pivot with the spring 2l pressing downwardly on the plunger at the right of this pivot, and therefore tending to rotate the plunger in a clockwise direction to the position shown in Fig. 2.

The plunger 20 has an inclined shoulder 40. If

the plunger is in cocked position, the sleeve Sv may be slid downwardly as to the position shown in Fig. 2, to cause the edge oi' the bore l2 to engage the inclined shoulder 40. Further downward movement of the sleeve will force the lower end of the plunger toward the right until it registers with the perforation I8', whereupon the spring 24 may expand and cause the plunger to pass through the perforation and enter the bore I4 of the ampule A. In the bore, it engages a follower 42 of rubber or the like back of the liquid in the bore, and causes such liquid to be discharged as a fine stream, indicated at 44, through the skin of the patient, indicated at 48, and enter the tissue therebeneath.

By preloading the spring 24 and providing a little distance for impact action when the plunger is released, I secure certain desirable injection characteristics, which will now be described. Impact'is secured by having the plunger 20 travel a small distance before it strikes the follower 42. This distance is represented by thethickness of the shoulder 30 in Fig. 2. The result is a sudden build-up of pressure when the plunger hits the follower, this build-up being to a greater point than possible with the compression of the spring 24 unaided by impact. For instance, the spring may be pre-loaded, so as to exert a pressure that, due to the relatively large size of the plunger 20 compared to the area of the orice it, produces 1000 pounds per square inch pressure of the stream of liquid 44, when only the spring pressure is applied against the follower through the plunger. Since the spring is pre-loaded, this pressure may reduce to only 800 or 850 pounds per square inch by the time the plunger is all the way down in the ampule, as shown in Fig. 3.

The impact action caused by some travel of the plunger before it strikes the follower producesA a sudden build-up of pressure at the time of impact, which may run eight or ten times as high as the pressure capable of being exerted by the spring alone. In other words, the .pressure of 'the stream 44 at the time of impact might be 8000 to 10000 pounds per square inch. This produces such force in the stream of liquid 44 that it readily passes through the skin without the necessity of having a needle for puncturing the skin.

After the puncture has been produced by the initial high Ypressure caused by impact, then the relatively lower pressure of 800 to 1000 pounds per square inch is sufdcient to maintain the stream 44, and cause substantially all of the liquid to pass through the perforation made in the skin and enter the tissue therebeneath. i

The spring pressure may, of course, be varied, so as to cause the injection to go to the proper depth in the tissue.

Another advantage of my present construction is the ease of cocking the spring. It is merely necessary to place the cap 26 in the palm of one hand and slide the sleeve S toward the cap with the other hand to effect the cocking operation. A fresh ampule A may then be placed in position and the collar l0 screwed onto the instrument for holding it there.

During the injection, the lcollar I0 is placed against the patients skin, as shown in Fig. 3, and the sleeve S slid toward the patient. The instrument is thereby held in close contact with the patient and the degree of contact is automatically regulated as it takes a predeterminedpressure on the sleeve before the plunger can be unlatched.

This pressure may be varied by changing the inclination at and thereby I am able to design an instrument, which will be operated for the injection only, when the proper pressure of the instrument against the patient has been performed. 'I'his also insures that the ampule A will be the proper distance from the skin or pressed against it with the proper pressure as required for different types of injections.

At the same time, the operation of the instrument is reduced toa ininimum number of steps and is very simple. Also the arrangement of the parts is such that the patient does not see what is happening in the instrument and is not affected detrimentally by the psychological reaction of actually observing the plunger quickly moving toward the ampule A, as in the spring operated hypodermic injectors of my previous applications.

Some changes may be made inthe arrangement and construction of the various parts of my hypodermic injector, without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims, any modified forms of construction or use of mechanical equivalents, which may be reasonably included within their scope.

'I claim as my invention:

l. In a hypodermic injector, an elongated casing, means at one end of said casing to contain liquid to be hypodermically injected, said means having a bore and a minute orifice, a plunger for entering said bore to displace liquid Vtherefrom through said minute orifice and thereby effect injection of the liquid to a subcutaneous position relative to a patient against which said casing is held, a pre-loaded spring in said casing for propelling said plunger, a sleeve slidable on said casing, said plunger being engageabie by said sleeve to compress said spring, means for latching said plunger in a position with said spring compressed to a still greater degree, said sleeve being operable, upon movement in an opposite direction, to unlatch said plunger and thereby' permit it to enter said bore and be propelled'therealong by expansion of said spring.

2. In a hypodermic injector, a casing, means at one end of said casing to contain liquid to be hypodermically injected, saidmeans having a bore and a minute orifice, a plunger for entering said bore to displace liquid therefrom through said minute orifice and thereby effect injection of the liquid to a subcutaneous position relative to a patient, a pre-loaded spring-.in said casing for propelling said plunger, a sleeve slidable on said casing, said plunger being engageable by said sleeve to further compress said spring, means for latching said plunger in a position with said spring so compressed, said sleeve being operable upon movement in an Opposite direction to unf latch said plunger and thereby permit it to enter said bore and be vpropelled.therealong by expansion of said spring to its pre-loaded position.

3. In a hypodermic injectorfan elongated casing, an ampule detachably mounted at one end of said casing to contain liquid to be hypodermically injected, said ampule having a bore-and a blunt end with a minute orifice in saidl blunt end, said vassegna engageable by said means upon movement thereofv in one direction to further compress said spring, means for latchng said plunger in a position with said spring so compressed and spaced from said follower, said means being operable by movement thereof in the opposite direction to unlatch said plunger and thereby permit it to enter said bore and-engage said follower with impact, due to expansion of said spring.

4. In a hypodermic injector, a casing, means at one end of said casing to contain liquid to be hypodermically injected, said means having a bore and a minute orifice, a plunger for entering said 'bore to displace liquid therefrom through said minute orifice, a spring in said casing for propelling said plunger, a sleeve slidable on said casing, said plunger being engageable by said sleeve to compress said spring, when the sleeve is slid in one direction, means for latching said plunger in a position with said spring compressed, said sleeve being operable, upon movement in an opposite direction, to unlatch said plunger and thereby permit it to enter said bore and -be propelled therealong by expansion of said spring.

5. A hypodermic injector comprising a casing, an ampule detachably mounted at one end thereoi' to contain liquid to be hypodermically` injected, said ampule having a bore and a minute oriilce, a plunger in said casing for entering said bore to displace liquid therefrom through said orice and thereby eiect self-injection of the liquid relative to a patient, a spring in said casing for propelling said plunger, a sleeve telescopically mounted on said casing, said plunger having a shoulder, and said sleeve having a projection for engaging said shoulder and moving said plunger to thereby compress said spring when said sleeve is moved in a direction away from said ampule, said casing having a shoulder, said plunger being engageable therewith when said spring has been so compressed for latching the plunger against movement under the bias of said spring, said projection being engageable with yan inclined portion of said plunger to disengage said plunger from said shoulder of said casing when said sleeve is moved in a direction toward said ampule and while the casing is held against a patient, whereby release of said plunger occurs at a predetermined pressure of the injector against the patient, whereupon said plunger enters said bore to be propelled therealong by expansion of said spring.

6. A hypodermic injector comprising an elongated casing, an ampule detachably mounted at oneend thereof to contain liquid to be hypodermically injected, said ampule having a, bore and a minute orice, a plunger in said casing for entering said bore to displace liquid therefrom through said orifice, a pre-loaded spring in said casing for propelling said plunger, a sleeve telescopically mounted on said casing, said plunger having a shoulder, and said sleeve having a projection for engaging said shoulder and moving said plunger to thereby increase the compression oi said spring when said sleeve is moved in a direction away from said ampule, said casing h'aving a shoulder, said plunger being engageable therewith when said spring has# been so compressed for latching the plunger against movement under the bias of said spring, said projection being engageable with said plunger to disengage it from said shoulder of said casing when said sleeve is moved in a direction toward said ampule.

'7. A hypodermic injector comprising an elongated caslng, an ampule detachably mounted at one end thereof to contain liquid to be hypodermically injected, a plunger in said casing to cooperate with said ampule and displace liquid therefrom, a pre-loaded spring in said casing for propelling said plunger, means telescopically mounted on said casing, said plunger having a sh'oulder, and said means engaging said shoulder and moving said plunger to thereby increase the compression of said spring when said means is moved in a direction away from said ampule, said casing having a shoulder, said plunger being engageable therewith when said spring has been so compressed for latching the plunger against movement under the bias of said spring, said means being engageable with said plunger to disengage it from said shoulder oi' said casing when said means is moved in a direction toward said ampule and while the casing is held against a patient.

8. A h'ypodermic injector comprising an elongated casing, detachable means associated therewith for containing liquid to be hypodermically injected, a plunger in said casing for entering said means and displacing the liquid therefrom, a spring in said casing for moving said plunger, said spring being so loaded that it is under compression when in released position and imder greater pressure when in a cocked position, a sleeve slidable on said casing in a direction away from said liquid container to cock said spring.

said sleeve being engageable with said plunger when sliding in the vopposite direction for releasing the plunger after predetermined pressure exerted through the sleeve and casing to the patient against which the casing is positioned, said plunger upon release permitting said spring to expand, and at the limit of its expansion still exerting force enough on the liquid to cause it to enter the puncture made in the skin by the initial pressure.

9. A hypodermic injector comprising a casing. detachable means associated therewith for containing liquid to be hypodermically injected, a plunger in said casing for entering said means and displacing the liquid therefrom, a spring in said casing for moving said plunger, said spring being so loaded that it is under compression when in released position and under greater pressure when in a cocked position, means slidable on said casing in a directionl away from said liquid container to cock said spring, said means being engageable with said plunger when sliding in the opposite direction for releasing the plunger after predetermined pressure exerted through the means and casing against a patient, said plunger upon release permitting said spring to expand and exert force enough on the liquid to cause substantially all of it to enter through a puncture made in the skin and enter the tissue therebeneath.

MARSHALL L. LOCKHART. 

